Add support for using arbitrary windows as wxStaticBox labels

This commit implements the new feature in wxGTK and updates the sample
and the documentation.

src/gtk/statbox.cpp

@@ -59,13 +59,14 @@ static gboolean expose_event(GtkWidget* widget, GdkEventExpose*, wxWindow*)
 // wxStaticBox
 //-----------------------------------------------------------------------------
 
-bool wxStaticBox::Create( wxWindow *parent,
-                          wxWindowID id,
-                          const wxString& label,
-                          const wxPoint& pos,
-                          const wxSize& size,
-                          long style,
-                          const wxString& name )
+bool wxStaticBox::DoCreate(wxWindow *parent,
+                           wxWindowID id,
+                           const wxString* labelStr,
+                           wxWindow* labelWin,
+                           const wxPoint& pos,
+                           const wxSize& size,
+                           long style,
+                           const wxString& name)
 {
     if (!PreCreation( parent, pos, size ) ||
         !CreateBase( parent, id, pos, size, style, wxDefaultValidator, name ))
@@ -74,11 +75,41 @@ bool wxStaticBox::Create( wxWindow *parent,
         return false;
     }
 
-    m_widget = GTKCreateFrame(label);
-    g_object_ref(m_widget);
+    if ( labelStr )
+    {
+        m_widget = GTKCreateFrame(*labelStr);
 
-    // only base SetLabel needs to be called after GTKCreateFrame
-    wxControl::SetLabel(label);
+        // only base SetLabel needs to be called after GTKCreateFrame
+        wxControl::SetLabel(*labelStr);
+    }
+    else // Use the given window as the label.
+    {
+        wxCHECK_MSG( labelWin, false, wxS("Label window can't be null") );
+
+        GtkWidget* const labelWidget = labelWin->m_widget;
+        wxCHECK_MSG( labelWidget, false, wxS("Label window must be created") );
+
+        // The widget must not have any parent at GTK+ level or setting it as
+        // label widget would fail.
+        GtkWidget* const oldParent = gtk_widget_get_parent(labelWidget);
+        gtk_container_remove(GTK_CONTAINER(oldParent), labelWidget);
+        gtk_widget_unparent(labelWidget);
+
+        // It also should be our child at wx API level, but without being our
+        // child in wxGTK, i.e. it must not be added to the GtkFrame container,
+        // so we can't call Reparent() here (not even wxWindowBase version, as
+        // it still would end up in our overridden AddChild()), nor the normal
+        // AddChild() for the same reason.
+        labelWin->GetParent()->RemoveChild(labelWin);
+        wxWindowBase::AddChild(labelWin);
+
+        m_labelWin = labelWin;
+
+        m_widget = gtk_frame_new(NULL);
+        gtk_frame_set_label_widget(GTK_FRAME(m_widget), labelWidget);
+    }
+
+    g_object_ref(m_widget);
 
     m_parent->DoAddChild( this );
 
@@ -121,16 +152,38 @@ void wxStaticBox::AddChild( wxWindowBase *child )
     wxStaticBoxBase::AddChild(child);
 }
 
+void wxStaticBox::WXDestroyWithoutChildren()
+{
+    // The label window doesn't count as our child, it's really a part of
+    // static box itself and it makes no sense to leave it alive when the box
+    // is destroyed, so do it even when it's supposed to be destroyed without
+    // destroying its children.
+    if ( m_labelWin )
+    {
+        // By deleting it here, we indirectly remove this window from the list
+        // of our children and hence prevent the base class version of this
+        // method from reparenting it and thus keeping it alive.
+        delete m_labelWin;
+        m_labelWin = NULL;
+    }
+
+    wxStaticBoxBase::WXDestroyWithoutChildren();
+}
+
 void wxStaticBox::SetLabel( const wxString& label )
 {
     wxCHECK_RET( m_widget != NULL, wxT("invalid staticbox") );
 
+    wxCHECK_RET( !m_labelWin, wxS("Doesn't make sense when using label window") );
+
     GTKSetLabelForFrame(GTK_FRAME(m_widget), label);
 }
 
 void wxStaticBox::DoApplyWidgetStyle(GtkRcStyle *style)
 {
     GTKFrameApplyWidgetStyle(GTK_FRAME(m_widget), style);
+    if ( m_labelWin )
+        GTKDoApplyWidgetStyle(m_labelWin, style);
     if (m_wxwindow)
         GTKApplyStyle(m_wxwindow, style);